WASHINGTON — Federal officials unleashed a series of legal assaults on the financial industry, targeting actions they said helped trigger the housing market collapse and then attempted to take advantage of desperate homeowners left in its wake.

The U.S. attorney’s office in Manhattan accused Wells Fargo of defrauding a government-backed mortgage insurance program of hundreds of millions of dollars over more than a decade by improperly underwriting more than 100,000 home loans.

At the same time, Attorney General Eric Holder and other officials announced the results of a yearlong effort to attack mortgage assistance scams. The Distressed Homeowner Initiative led to criminal charges against 530 people accused of defrauding about 73,000 underwater homeowners nationwide of an aggregate $1 billion.

The initiative also led to 110 federal civil cases against more than 150 defendants who allegedly bilked an additional 15,000 victims out of $37 million in financial losses through phony mortgage-assistance schemes.

“Put simply, these comprehensive efforts represent an historic, governmentwide commitment to eradicating mortgage fraud and related offenses around the country,” Holder said Tuesday at a news conference.

The suit seeks “hundreds of millions of dollars” in damages for claims the Department of Housing and Urban Development has paid to cover defaulted loans “wrongfully certified” by Wells Fargo.

Adding “accelerant to a fire,” said U.S. Attorney Preet Bharara, was a Wells Fargo bonus system that rewarded employees based on the number of loans approved.

The lawsuit alleges the bank failed to properly underwrite more than 100,000 loans it certified to be eligible for FHA insurance. When Wells Fargo discovered problems with the loans, it failed to notify HUD, as required, the suit said.